This invention relates to systems for recharging batteries used for vehicle propulsion.
Although battery driven vehicles have many obvious advantages, they have a severe drawback in that the energy available for propulsion is limited to the amount of energy which can be stored in the batteries. As a consequence, batteries with as large a capacity as possible are used, with battery weight serving as a limitation to the maximum size of the battery which can be carried by the vehicle. Typically, a 108 volt, 200 ampere-hours battery may be used for such purposes.
Because of the constraints imposed by battery size, the batteries must be frequently recharged, and it is to the battery charging problems that the present invention is addressed.
It is desirable to carry the battery charging equipment with the vehicle so that it can be plugged into any conventional a-c power source (and preferably regardless of whether such source be 120 or 240 volts) rather than being restricted to locations having battery chargers thereat.
Since it is to be carried with the vehicle the battery charging equipment should have a low weight and occupy a low volume of space. This poses significant problems because the onboard equipment must be capable of handling and controlling high currents so that the battery may be charged in a reasonably short period to time. Such equipment must also include components to enable the motor control circuits to be changed from a power mode, wherein the battery is connected to drive the motor, to a charging mode wherein the battery is connected to the charger. Further, since an onboard charging apparatus would be needed for each vehicle, it should be inexpensive and utilize as much of the power mode components as possible for the control of the battery charging function.
Prior art attempts have made some dual use of onboard electronics for power and charging modes but have accomplished their results by use of a relatively large number of mechanical power contactors to reconfigure the power circuits from power mode to charging mode. An example of such an attempt is that disclosed in U.S. Pat. No. 4,008,423, issued to C. C. Christianson et.al. on Feb. 15, 1977. Since mechanical contactors are relatively bulky, heavy and expensive, this approach provides but a limited solution to the problem.
It is an object of the present invention to provide a battery charging circuit for use with a battery driven motor which utilizes the power mode components for control of battery charging current and which reconfigures the power circuits from power mode to charging mode by use of inexpensive and lightweight components.
it is a further object of the present invention to provide a battery charging circuit for use with a battery driven motor wherein the battery is connectable to the motor for normal power mode operation of the motor or connectable to a battery charger for normal charging of the battery and wherein damage to the system will not occur if the motor is connected to the battery during charging of the battery.